Field of the Invention
The invention relates to the field of the wastewater treatment, and more particularly to a denitrification biofilter device and a method for treating wastewater.
Description of the Related Art
Denitrification biofilter is used for deep treatment of nitrogen in wastewater. The principle of the denitrification biofilter is that a biofilm adhering on a filler in a reactor is utilized to reduce nitrite and nitrate into nitrogen, nitric oxide, or nitrous oxide in anoxic condition (in the absence of molecular dissolved oxygen).
It has been found that the existence of oxygen inhibits nitrogen removal effect in the denitrification and increases the nitrite in the effluent. As dissolved oxygen widely exists in a secondary effluent, the dissolved oxygen in an influent results in a large consumption of external carbon source of the denitrification biofilter, thereby increasing the operation costs. Furthermore, the conventional denitrification biofilters have a limited removal rate of ammonia nitrogen in the wastewater, and a total nitrogen concentration in the effluent is always unstable due to the affection of the ammonia nitrogen load in the influent.
A typical denitrification biofilter device for controlling the addition of the carbon source includes a denitrification biofilter. The denitrification biofilter is provided with an online influent nitrate sensor, an online influent dissolved oxygen sensor, an online effluent nitrate sensor, a nitrate analyzer, a dissolved oxygen analyzer, a process controller, an industrial control computer, a carbon source tank, a variable frequency carbon source pump, and a carbon source flowmeter. And a corresponding method for controlling the addition of the carbon source includes: 1) water introduction; 2) parameter treatment and judgment; 3) frequency treatment by a frequency converter; 4) dosing control of the carbon source; 5) stable operation process; 6) failure diagnosis; and 7) backwashing process. The device and the corresponding method are adapted to deep wastewater treatment and nitrogen-containing industrial wastewater treatment.
Another typical device for treating a secondary effluent of urban sewage includes a denitrification biofilter device. The denitrification biofilter device is provided with a carbon source tank, a variable frequency dosing pump for regulating the flow, and a pipe. The regulation of the variable frequency dosing pump is conducted to control the addition of the carbon source according to an online nitrate nitrogen concentration meter and an online chemical oxygen demand (COD) concentration meter.
The above devices and methods are designed on the purpose for controlling the production costs by optimization of the addition of the carbon source, however, the dissolved oxygen of the influent is not decreased, the consumption of the carbon source is large, the production cost is still high, and a large amount of the carbon source is wasted.